The present invention relates to a device for the recognition of binary locking words in a digital train.
Such devices are applied in particular to demultiplexers with high output, for example 34 Mbits/s, 140 Mbits/s.
In multiplexed digital trains, the frames are separated from one another by frame locking words. A frame may, for example, comprise four sectors of 96 groups of 4 binary elements. In this case, the frame locking word associated with each frame occupies the first 10 bits of the first three groups of the first sector, two being in reserve. Demultiplexing includes the identification at reception of each of the trains and each of the frames and the frame locking words in the trains received.
Notice G 742 of the CCITT recommends, as frame locking word, or signal, the word 1111010000.
At reception, it is necessary to be able to identify such a word with certainty, without, however, wasting too much time in recognizing and decoding such a long word.
It is already known to identify such a word of 10 binary elements with the aid of a device incorporating ten flip flops mounted in registers.
However, such a quantity of flip flops prohibits recognition of the word on a component of very small dimensions, such as a chip.
It is therefore an object of the present invention to reduce the number of logic elements in the devices employed heretofore.